implement and test GroupsCore interface for FreeGroup and FPGroup

Project.toml

@@ -9,6 +9,7 @@ DataStructures = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 GroupsCore = "d5909c97-4eac-4ecc-a3dc-fdd0858a4120"
 KnuthBendix = "c2604015-7b3d-4a30-8a26-9074551ec60a"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 ThreadsX = "ac1d9e8a-700a-412c-b207-f0111f4b6c0d"
 
 [compat]

src/new_types.jl

@@ -61,6 +61,8 @@ function Base.rand(rng::Random.AbstractRNG, rs::Random.SamplerTrivial{<:Abstract
     return FPGroupElement(word_type(G)(rand(1:nletters, l)), G)
 end
 
+Base.isfinite(::AbstractFPGroup) = (@warn "using generic isfinite(::AbstractFPGroup): the returned `false` might be wrong"; false)
+
 ## FPGroupElement
 
 mutable struct FPGroupElement{G<:AbstractFPGroup,W<:AbstractWord} <: GroupElement
@@ -109,7 +111,7 @@ function Base.:(*)(g::FPGroupElement, h::FPGroupElement)
     return FPGroupElement(word(g) * word(h), parent(g))
 end
 
-GroupsCore.isfiniteorder(g::FPGroupElement) = isone(g) ? true : throw("Not Implemented")
+GroupsCore.isfiniteorder(g::FPGroupElement) = isone(g) ? true : (@warn "using generic isfiniteorder(::FPGroupElement): the returned `false` might be wrong"; false)
 
 # additional methods:
 Base.isone(g::FPGroupElement) = (normalform!(g); isempty(word(g)))
@@ -138,6 +140,12 @@ Base.show(io::IO, F::FreeGroup) = print(io, "free group on $(ngens(F)) generator
 KnuthBendix.alphabet(F::FreeGroup) = F.alphabet
 relations(F::FreeGroup) = Pair{eltype(F)}[]
 
+# GroupsCore interface:
+# these are mathematically correct
+Base.isfinite(::FreeGroup) = false
+
+GroupsCore.isfiniteorder(g::FPGroupElement{<:FreeGroup}) = isone(g) ? true : false
+
 ## FP Groups
 
 struct FPGroup{T,R,S} <: AbstractFPGroup

test/fp_groups.jl

@@ -41,4 +41,9 @@
     New.normalform!(h)
     @test h == H([5])
 
+    @testset "GroupsCore conformance: H" begin
+        test_Group_interface(H)
+        test_GroupElement_interface(rand(H, 2)...)
+    end
+
 end

test/free_groups.jl

@@ -62,4 +62,9 @@
         @test New.word(last(E8)) == Word([6])^8
     end
 
+    @testset "GroupsCore conformance" begin
+        test_Group_interface(F3)
+        test_GroupElement_interface(rand(F3, 2)...)
+    end
+
 end

test/runtests.jl

@@ -28,6 +28,9 @@ using LinearAlgebra
       using Groups.New
       using KnuthBendix
 
+      using GroupsCore
+      include(joinpath(pathof(GroupsCore), "..", "..", "test", "conformance_test.jl"))
+
       include("free_groups.jl")
       include("fp_groups.jl")
    end